Objective:

This research seeks to identify how nitrosamines form and decompose in amine scrubbing. It also will attempt to determine what factors can be controlled to limit nitrosamine accumulation and what the impact of nitrosamine emissions is on the environment.

Approach:

Nitrosamine formation and decomposition will be studied through bench-scale experiments that mimic absorber and stripper conditions. Specifically, simulated flue gas with nitrogen oxides will be sparged through amine solutions and analyzed for absorbed species. The solution will then be heated to stripper temperatures ranging from 120 °C to 150 °C to analyze for nitrosamine content. Final results will be modeled for conditions at the pilot plant and compared to current data from the pilot plant. The model will then be refined based on any discrepancies between pilot-plant and bench-scale results. The final model will give an expected nitrosamine concentration based on the amine scrubber and the inlet flue gas. This concentration can be used by EPA and the industry to help set regulations on nitrosamine emissions and determine process conditions.

Expected Results:

Nitrosamine formation will be dominated by NO2 absorption into the amine as nitrite. The nitrite will then travel to the stripper, where it can react with the amine to form nitrosamines. NO is not expected to be reactive, so eliminating NO2 from the NOx emissions should drastically reduce nitrosamines. Nitrite also might be able to form directly from amine oxidation. Thus, amine scrubbers running with a NOx-free flue gas might still have small amounts of nitrosamines. Nitrosamines should decompose in the stripper, leading to a steady-state concentration, in which formation from NO2 balances with decomposition. The steady-state nitrosamine concentration can then be used to determine the environmental impact of nitrosamine emissions from the amine scrubber, either through volatile nitrosamine loss or through solvent spills.

Potential to Further Environmental/Human Health Protection

Amine scrubbing is currently the preferred technology for carbon capture from pilot plants, and the first-generation carbon capture units are likely to be amine scrubbers. Recognizing the harmful byproducts formed during amine scrubbing will ensure that these units are industrially hygienic and keep the population around these plants healthy.

Supplemental Keywords:

amine scrubbing, carbon management, nitrosamine

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.